How Do I Get Data from JSON Format in Javascript

I’ve been struggling with how to retrieve data from a JSON structured response to a query of a Sony Bravia TV. I’ve tried SEVERAL syntax variations to get just a single element’s data, but no joy.

The response is sent to a textarea field having the id "log". Here is what gets displayed:

{
    "result": [
    [
        {
            "target": "speaker",
            "volume": 22,
            "mute": false,
            "maxVolume": 100,
            "minVolume": 0
        }
    ]
            ],
    "id": 1
}

The javascript function is below. In the last line, I’m trying to see a single element, but get nothing. What should the last line be?

    var gblJSONresponse = [];
    function send(service, method, params) {
        var ip = 'xxx.xxx.xxx.xxx';
        var psk = 'xxxx';
        var xhr = new XMLHttpRequest();
        xhr.onload = function() {
            var resp = xhr.responseText;
            gblJSONresponse = JSON.parse(xhr.response);
            log(JSON.stringify(JSON.parse(xhr.response), null, '  '));
        };

        xhr.open('POST', 'http://' + ip + '/sony/' + service);
        if (psk) {
            xhr.setRequestHeader('X-Auth-PSK', psk);
        }

        xhr.send(JSON.stringify({
            method: method,
            version: '1.0',
            id: 1,
            params: params ? [params] : [],
        }));

        window.alert("JSONresponse:n"+JSONresponse[0].result[0].target);
    }